The long term goal of this laboratory is to understand the pathophysiology of limbic epilepsy (LE) at the molecular level. External influences can produce permanent plasticity changes in normal neuronal tissue that cause spontaneous recurrent epileptiform discharges (SREDs) in hippocampal neuronal networks. This research effort has discovered that the induction of epileptogenesis in several models of LE caused a long term increase in the expression of Ca2+-regulated transcription factors (TFs) that were associated with decreased expression in the gamma-amino-butyric acid (GABA)A receptor (GABAAR) alpha subunit gene expression. These findings may have considerable significance in understanding the molecular mechanisms that cause LE and will be the focus of this research proposal. The Central Hypothesis to be tested in this research effort is that epileptogenesis in three models of LE produces an altered "epileptic" neuronal phenotype characterized by long lasting alterations in the regulation of [Ca2+]i levels that induce persistent changes in the expression o specific TFs that in turn regulate the expression of several somatic genes, including the expression of specific subunit isoforms of the GABAA receptor that ultimately play a role in producing alterations in neuronal excitability and the development and maintenance of SREDs. A corollary to this hypothesis is that NMDA receptor activation during epileptogenesis elevates [Ca2+]i levels (induction), which in turn causes persistent decreases in CaMKII activity that in turn changes the ability of "epileptic" neuron to release and uptake Ca2+i from intracellular sources, resulting in long lasting increased [Ca2+]i levels in both the cytoplasm and nucleus (maintenance) maintaining some of the long term plasticity changes associated with epileptogenesis. This research project will combine the multi-disciplinary approaches of molecular genetics, biochemistry, and electrophysiology to study 3 models of LE and to accomplish the following Specific Aims: Aim 1: Determine whether NMDA receptor activated increased [Ca2+]i during epileptogenesis causes the long lasting changes in the development of SREDs and the decreased genetic expression and function of GABAAR; Aim 2: Determine whether long lasting changes in the expression of specific NMDA/Ca2+-regulated TFs occur during the induction and maintenance of SREDs; Aim 3: Evaluate whether the NMDA/Ca2+-induced changes in TF expression that occur in epileptogenesis cause the long term changes in GABAAR gene expression and function and the development of SREDs; Aim 4: Determine if [Ca2+]i homeostatic mechanisms are altered in a NMDA/Ca2+ manner during epileptogenesis and contribute to the maintenance of SREDs, decreased GABAAR gene expression and function and increased TF expression; Aim 5: Evaluate the molecular mechanisms causing long-term alterations in [Ca2+]i homeostasis and determine their role in regulating TF expression and GABAAR gene expression and function. Results from this study may elucidate some of the molecular mechanisms that regulate the persistent reductions of GABAAR gene expression and function and will provide an insight into the pathophysiology of LE and may offer new treatment strategies and opportunities to prevent this debilitating condition. Results from this study may elucidate some of the molecular mechanisms that regulate the persistent reductions of GABAAR gene expression and function and will provide an insight into the pathophysiology of LE and may offer new treatment strategies and opportunities to prevent this debilitating condition.